1. Field of the Invention
This invention is in the field of protective caps for small caliber Armor-Penetrating Fin-Stabilized Discarding-Sabot (APFSDS) ammunition. The purpose of such caps is to protect the fin stabilized penetrator during rough handling including feeding and chambering a round in an automatic cannon to maintain undamaged the smooth surface at the forward end of the penetrator so that the trajectory of the fin stabilized penetrator, or projectile, does not significantly deviate from its predicted trajectory.
2. Description of the Prior Art
Conventional small-caliber APFSDS projectile consists of a fin-stabilized, armor piercing penetrator which is supported in the bore of an automatic cannon by means of a multiple segment two-piece sabot. Typically, the penetrator has a cylindrical body portion measuring approximately 8.3 mm in diameter, and a leading portion which tapers to a fine point for low aerodynamic drag. It is crucial that the point of the penetrator be wellprotected, since mishandling can result in the point becoming dented scratched or bent. Damage of this nature is clearly undesirable, since any irregularities in the streamlined surface of the penetrator will significantly increase its aerodynamic drag and thus, cause its trajectory to deviate significantly from its predicted trajectory which is based on the assumption that the leading, or tapered front, end portion of the penetrator will not be dented, scratched, or bent.
To prevent such damage from occurring, the projectile is normally provided with a one-piece protective cap which is fastened to the front end of the sabot. The cap protects the tapered front end of the penetrator during rough handling and provides a smooth surface at the forward end of the ammunition so that a cartridge which includes a sabot and penetrator will feed and chamber in an automatic cannon without damaging the penetrator. In addition, the cap is designed to separate from the sabot and the sabot from the projectile as the projectile exits the muzzle of a cannon in such a way that neither the cap nor the sabot interferes with the flight of the projectile.
In the past, such one-piece protective caps have been molded from polyethylene. Typically, such caps are molded with a reduced-diameter section enabling them to be snap-fit over a cooperating lip portion of the sabot. When a cartridge fitted with one of these caps is fired from an automatic cannon, a combination of air ram pressure and centrifugal force causes the cap to split and detach from the sabot thus allowing the projectile to fly unimpeded, or without deviating from its desired trajectory.
It has been found, however, that conventional polyethylene caps do not function as effectively as desired. They separate prematurely from the sabot during rough handling, leaving the tapered portion of the penetrator unprotected. At other times, they have failed to split and detach from the sabot or have fragmented in such a way as to disturb the flight of the projectile. Thus, the accuracy and effectiveness of the projectile has been impaired.
Therefore, a need exists for a new and improved protective cap for small-caliber APFSDS ammunition, which provides better protection of the penetrator during handling, and which breaks apart "cleanly" at muzzle exit, detaching from the projectile without significantly disturbing the flight of the projectile and thus adversely affecting its accuracy, predicted trajectory, and its terminal velocity and, thus, its ability to penetrate a target.